Method for synchronizing a receiver with a transmitter

ABSTRACT

A first synchronization signal having a multitude of second synchronization signals, which are removed from a set of second synchronization signals that is subdivided into code sets, is transmitted by a transmitter to a receiver. According to the invention, the multitude of second synchronization signals, which are transmitted with the first synchronization signal, are specified by a code set, whereby the code sets are grouped into used and unused code sets, and whereby the set of second synchronization sequences is subdivided into code sets such that the maximum of the peak values of the cross-correlation functions of the second synchronization signals, which are specified by a used code set, with the first synchronization signal is minimal.

[0001] The invention relates to a method for synchronizing a receiverwith a transmitter, in particular within a mobile radio network.

[0002] The rapid technical development in the field of mobilecommunications has led in recent years to the development of new mobileradio systems of the third generation. An essential role is played inthis case by the so-called UMTS (Universal Mobile TelecommunicationsSystem), which is based at least partly on the WCDMA (Wideband CodeDivision Multiple Access) technology. The air interface of this system,UTRA (UMTS Terrestrial Radio Access), forms a central element in thissystem. This air interface can be implemented in accordance with theprior art by means of two different types of duplex, TDD (Time DivisionDuplex) and FDD (Frequency Division Duplex) respectively.

[0003] For the purpose of synchronizing a receiver (mobile station,subscriber station) with a transmitter (base station), it is known totransmit a first synchronization signal (synchronization sequence,synchronization code, code word) PSC (Primary Synchronization Code) fordetecting a cell and/or a base station, and second synchronizationsignals (synchronization sequence, synchronization code, code word) SSC(Secondary Synchronization Codes) for the purpose of identifyingdifferent parameters of the detected cell and/or base station from thetransmitter (base station) to the receiver (mobile station). Such asynchronization is also called cell search.

[0004] It is also known in this case from [1] and [5] to use the samePSC and the same SSCs for UTRA FDD and UTRA TDD.

[0005] However, the situation arises in this case that for the purposeof synchronization with subscriber stations UTRA FDD requires the use of16 different SSCs, whereas for the purpose of synchronization withsubscriber stations UTRA TDD requires the use of only different SSCs.

[0006] The set of 16 SSCs is grouped in UTRA TDD into the five codesets, of which four code sets, which each include three SSCs, are usedin UTRA TDD for synchronization, and one code set, which includes fourSSCs, is not used in UTRA TDD for synchronization. Three SSCs of a codeset are emitted for synchronization purposes in parallel with the PSC inthe time slots to which a PSCH (Primary Synchronization Channel) isassigned.

[0007] The PSC is a so-called “Generalised hierarchical Golay Sequence”with good aperiodic autocorrelation properties that is known per se from[2].

[0008] The PSC is accordingly defined by the following constructionrule, in particular:

[0009] Let a=<x₁, x₂, x₃, . . . , x₁₆>=<1, 1, 1, 1, 1, 1, −1, −1, −1, 1,−1, 1, −1, 1, 1, −1> be a sequence of 16 elements.

[0010] The PSC is then generated by modulating ‘a’ with the aid of acomplementary Golay sequence. The sequence a is therefore repeated, andwith each repetition all the elements of the sequence a are multipliedby the value, corresponding to the repetition, of the complementaryGolay sequence. Subsequently, all the elements are multiplied by thecomplex number (1+j). This generates a complex sequence that hasidentical real and imaginary parts.

[0011] The PSC C_(p) is therefore defined as:

[0012] C_(p)=<y(0), y(1), y(2), . . . , y(255)>, wherein it holds that:

[0013] y=(1+j)×<a,a,a,−a,−a,a,−a,−a,a,a,a,−a,a,−a,a,a>; the value withthe smallest index y(0) corresponds in this case to the first symbol orchip transmitted in a time slot.

[0014] The 16 SSCs {C₀, . . . , C₁₅}, which are likewise known from [5],are based on Hadamard sequences that are formed by every 16th row,starting with row 0, of a positionally scrambled Hadamard matrix H₈.They are likewise complex sequences that have identical real andimaginary parts.

[0015] In particular, the 16 SSCs are formed as follows:

[0016] The 16 SSCs (SSC code words) {C₀, . . . , C₁₅} can be obtained bymeans of a positional multiplication of a Hadamard sequence by thesequence z that is defined as

[0017] z=<b,b,b,−b,b,b,−b,−b,b,−b,b,−b,−b,−b,−b,−b>, wherein it holdsthat:

[0018] b=<x₁, . . . ,x₈,−x₉, . . . ,−x₁₆>=(1, 1, 1, 1, 1, 1, −1, −1, −1,1, −1, 1, −1, 1, 1, −1>;

[0019] The Hadamard sequences are defined as rows of the matrix H₈, H₈being determined by the following recursive definition: H₀ = (1)${H_{k} = \begin{pmatrix}H_{k - 1} & H_{k - 1} \\H_{k - 1} & {- H_{k - 1}}\end{pmatrix}},{k \geq 1}$

[0020] The rows are enumerated from the top down, starting with 0 forthe first row (that is the row containing only ones).

[0021] The nth Hadamard sequence is now defined as the nth row of H₈,the rows being enumerated in sequence from the top down with n=0, 1, 2,. . . , 255.

[0022] Let h_(m)(i) and z(i) respectively be the ith symbol of thesequence h_(m) and z, respectively, wherein i=0, 1, 2, . . . , 255, andwherein i=0 refers to the symbol recorded furthest left.

[0023] The ith SCH code word, C_(SCH,i), wherein i=0, . . . , 15 is thendefined as C_(SCH), i=(1+j)×<h_(m)(0)×z(0), h_(m)(1)×z(1),h_(m)(2)×z(2), . . . , h_(m)(255)×z(255)>, wherein m=(16×i) and thesymbol recorded furthest left corresponds to the symbol or chip that isfirst emitted.

[0024] Such an SCH code word is defined for each 16th row of the matrixH₈; this yields a total of 16 different SCH code words.

[0025] The SSCs, {C₀, . . . , C₁₅}, are now defined by these SCH codewords, C_(SCH,i), as: C_(i)=C_(SCH,i), i=0, . . . , 15.

[0026] 1. The second synchronization sequences are also denoted belowwith the aid of SSCi or SSC_(i), wherein it holds that:

[0027] SSCi=SSC_(i)=C_(i)=C_(SCH,i), i=0, . . . , 15;

[0028] Since, now, one PSC and three SSCs of a code set are emitted inparallel for synchronization purposes, and correlation calculations arecarried out at the receiving end for the purpose of synchronization, thegrouping of the set of the SSCs to form code sets has an influence onthe quality of and the outlay on these correlation calculations, andthus the synchronization or the cell search.

[0029] An improved grouping of SSCs to form used code sets is proposedin [5], in which the grouping was determined simply with the aid of thesequence of the SSCs:

[0030] Code set 1: SSC₀, SSC₁, SSC₂

[0031] Code set 2: SSC₃, SSC₄, SSC₅

[0032] Code set 3: SSC₆, SSC₇, SSC₈

[0033] Code set 4: SSC₉, SSC₁₀, SSC₁₁

[0034] The following grouping of SSCs to form used code sets is proposedin [1], in which the grouping was performed using the following rules:

[0035] a) select as used SSCs the 12 SSCs from the possible 16 that havethe smallest RMS (Root Mean Square) value of the cross correlationrelative to the PSC. The RMS value in this case denotes the root of themean square of the CCF (cross-correlation function) of the SSC's withthe PCS. This rule is based on the following finding: if a high crosscorrelation exists between an SSC and the PCS, it is possible that, inthe search for the PSC that is typically carried out by a correlation ofthe received signal with the PSC, the mobile station could erroneouslydeclare such a high cross correlation with the SSC as PSC.

[0036] b) These 12 SSCs are grouped into code sets in such a way thatthe mean RMS value for all three SSCs located in a code set is alsominimized for the worst group.

[0037] The following grouping of SSCs to form used code sets resulted in[1] from the application of these criteria:

[0038] Code set 1: SSC₅, SSC₈, SSC₁₁

[0039] Code set 2: SSC₀, SSC₁, SSC₁₅

[0040] Code set 3: SSC₁₂, SSC₁₃, SSC₁₄

[0041] Code set 4: SSC₄, SSC₆, SSC₁₀.

[0042] However, as will be set forth later on, this selection is notoptimal.

[0043] The invention is now based on the object of specifying a methodfor synchronizing a receiver with a transmitter, and a method for cellsearch that permits reliable synchronization.

[0044] This object is achieved by means of the features of theindependent claims. Advantageous and expedient developments follow fromthe dependent claims.

[0045] Thus, according to the invention for the purpose of synchronizinga receiver with a transmitter, in which a first synchronization signalwith a multiplicity of second synchronization signals is transmittedfrom the transmitter to the receiver, a set of second synchronizationsignals being subdivided into used code sets and at least one unusedcode set in such a way that the maximum in the peak values of thecross-correlation functions of the second synchronization signals, whichare determined by a used code set, with the first synchronization signalis minimal.

[0046] The transmission of a first synchronization signal “with” secondsynchronization signals also in this case comprises the transmission ofindividual second synchronization signals (for example sequentially),several or all second synchronization signals of a code set beingperformed performed during the transmission of the first synchronizationsignal.

[0047] The invention relates in this case, in particular, to the UTRATDD mode; the use of second synchronization signals of an unused codeset in the UTRA FDD mode even while the PSC is being emitted istherefore not excluded. The invention also comprises the case that theunused second synchronization signals are not regarded as a code set.

[0048] The invention is based in this case on the finding that the RMS(Root Mean Square Value) of the cross-correlation functions CCF is lessrelevant than the peak value in the CCF.

[0049] This is based, in turn, firstly on the requirement for a quick orshort PSC search, which has to be carried out as quickly as possible forthe following three reasons:

[0050] The PSC correlation requires a continuous activation of the radiosection and a continuous, high computing power of the baseband sectionof the mobile station. Consequently, a fast PSC search is required tosave energy.

[0051] During the first cell search, the frequency of the localoscillator has not yet been calibrated by the signal of the basestation, but generally has an increased frequency error. However, anexisting frequency error displaces the time base of the mobile stationrelative to the time base of the base station. It is thereforeimpossible to accumulate the correlation of the PSC over a lengthy timeperiod and thereby, for example, to obtain a reliable result byaveraging.

[0052] A maximum in the correlation that is used for the PSC search,that is to say a potential candidate for the PSC search, is verifieddirectly by virtue of the fact that the second and, further, also thethird stage of the cell search are carried out with the aid of thishypothesis for the time pattern derived from this maximum. This is moreefficient than simply carrying out the PSC correlation and accumulationfor a longer time.

[0053] Consequently, the portion of the superimposed noise is stillrelatively high in the case of the PSC search (search for a maximum inthe PSC correlation) under these special boundary conditions of a shortPSC search. The cross correlations of the PSC with the SSCs are,however, not relevant when they lie below this typically high noiselevel, and will lead to a significant worsening of detection only whenthey lie above this level. The probability of erroneous detection risesexponentially with the magnitude of a CCF maximum. Consequently, onlythe greatest CCF maxima contribute significantly to the erroneousdetection.

[0054] As a result of the invention, the first stage of thesynchronization, that is to say the detection of a cell or a basestation with the aid of a PSC, is performed reliably, in particular morereliably than in the prior art.

[0055] An essential finding on which this invention is based istherefore that, by contrast with the concept on which the proposal [1]is based, what is important is not to minimize the mean RMS value of thecross-correlation functions CCF [lacuna] used SSCs with the PSC within acode set of SSCs, but to minimize the maximum in the peak value of thecross-correlation functions of the used SSCs with the PSC.

[0056] One refinement of the invention provides to undertake theassignment of SSCs to the first code set in such a way that the maximumvalue of the peak values in the CCF of the SSCs, assigned to the firstcode set, with the PSC is as low as possible, and then the samecriterion for the selection from the SSCs still not assigned to any codeset is used for the following code sets.

[0057] This refinement is based on the finding that the grouping,selected in [1], of the SSCs into code sets in such a way that the RMSis as low as possible within a code set even for the worst code setleads to a lower reliability of synchronization than ensuring that themaximum value of the peak values in the CCF for the first code set is aslow as possible, and then making use for the further code sets of thesame criterion for the selection from the SSCs still not assigned to anycode set.

[0058] One advantageous development of the invention provides forcarrying out the grouping of the second synchronization sequences asfollows:

[0059] Code set 1: SSC1, SSC3, SSC5;

[0060] Code set 2: SSC10, SSC13, SSC14;

[0061] Code set 3: SSC0, SSC6, SSC12;

[0062] Code set 4: SSC4, SSC8, SSC15.

[0063] This leads to the following unused second synchronizationsequences and to the following unused code set:

[0064] SSC2, SSC7, SSC9, SSC11.

[0065] Complicated simulations with the aid of simulation tools set upspecially for this purpose lead in the case of the application of thecriteria according to the invention to this special grouping of secondsynchronization sequences. Appropriate results are summarized in thefollowing tables: TABLE 1 maximum peak values in the CCF of therespective code set of the SSCs for a grouping into code sets inaccordance with an advantageous refinement of the invention: select theSSCs with the lowest peak value in the CCF with the PSC; group the SSCsthus selected in such a way relative to code sets that the maximum ofthe peak values in the CCF of the SSCs is minimized within each codeset. CCF of SSC Maximum peak with PSC value in the CCF Code Peak of therespective set value RMS code set of the SSCs 1 SSC₅ 67 9.93 75 SSC₁ 6711.28 SSC₃ 75 12.58 2 SSC₁₄ 77 11.87 79 SSC₁₀ 77 11.24 SSC₁₃ 79 11.48 3SSC₁₂ 79 11.62 81 SSC₆ 79 11.65 SSC₀ 81 10.49 4 SSC₁₅ 83 11.48 89 SSC₈83 12.10 SSC₄ 89 11.90 Unused SSC₁₁ 99 10.46 SSC₇ 99 12.91 SSC₉ 10912.31 SSC₂ 111 12.13

[0066] TABLE 2 maximum peak values in the CCF of the respective code setof the SSCs for a grouping into code sets in accordance with [1]. CCF ofSSC Maximum peak with PSC value in the Code Peak CCF of the respectiveset value RMS code set of the SSCs 1 SSC₅ 67 9.93 99 SSC₈ 83 12.10 SSC₁₁99 10.46 2 SSC₀ 81 10.49 83 SSC₁ 67 11.28 SSC₁₅ 83 11.48 3 SSC₁₂ 7911.62 79 SSC₁₃ 79 11.48 SSC₁₄ 77 11.87 4 SSC₄ 89 11.90 89 SSC₆ 79 11.65SSC₁₀ 77 11.24 Unused SSC₂ 111 12.13 SSC₃ 75 12.58 SSC₇ 99 12.91 SSC₉109 12.31

[0067] TABLE 3 maximum peak values in the CCF of the respective code setof the SSCs for a grouping into code sets in accordance with [5]. CCF ofSSC Maximum peak with PSC value in the Code Peak CCF of the respectiveset value RMS code set of the SSCs 1 SSC₀ 81 10.49 111 SSC₁ 67 11.28SSC₂ 111 12.13 2 SSC₃ 75 12.58 89 SSC₄ 89 11.90 SSC₅ 67 9.93 3 SSC₆ 7911.65 99 SSC₇ 99 12.91 SSC₈ 83 12.10 4 SSC₉ 109 12.31 109 SSC₁₀ 77 11.24SSC₁₁ 99 10.46 Unused SSC₁₂ 79 11.62 SSC₁₃ 79 11.48 SSC₁₄ 77 11.87 SSC₁₅83 11.48

[0068] TABLE 4 summary of the maximum peak values in the CCF for eachcode set for the three proposals. Maximum peak values in the CCF of thecomplete set of the SSCs Design variant of the Proposal in Currentinvention [1] specification 89 99 111 81 89 109 79 83 99 75 79 89

[0069] Another development of the invention provides that for thepurpose of synchronization the transmitted synchronization sequences arefurther processed at the receiving end, for example in a mobile station,in particular in the form of correlation calculations.

[0070] The invention is described below by way of example with the aidof a UMTS mobile radio system, reference being made to the followingFIGURE:

[0071]FIG. 1 block diagram of the principle of a mobile radio system.

[0072] Illustrated in FIG. 1 is a cellular mobile radio network thatconstitutes, for example, a UMTS (Universal Mobile TelecommunicationSystem) system that comprises a multiplicity of mobile switching centersMSC that are networked together and furnish the access to a fixednetwork. Furthermore, these mobile switching centers MSC are connectedto in each case at least one base station controller BSC that can alsobe formed by a data processing system.

[0073] Each base station controller BSC is connected, in turn, to atleast one base station BS. Such a base station BS is a radio stationthat can set up a radio link to other radio stations, so-called mobilestations MS, via a radio interface. Information can be transmitted bymeans of radio signals between the mobile stations MS and the basestation BS assigned to these mobile stations MS. The range of the radiosignals of a base station, or a plurality thereof in the individualcase, essentially define a radio cell.

[0074] Base stations BS and a base station controller BSC can becombined to form a base station system. The base station system is alsoresponsible in this case for the radio channel administration and/orallocation, the data rate matching, the monitoring of the radiotransmission link, handover procedures, and for the allocation of thespread code sets to be used, and communicates the signaling informationrequired therefor to the mobile stations MS.

[0075] The UMTS system and the corresponding components of mobilestations and/or base stations can communicate in this case in theUTRA-TDD mode and/or in the UTRA-FDD mode.

[0076] The base stations BS emit a first synchronization signal PSC fora first cell search or the first step of a synchronization of a basestation with a mobile station. In parallel with the PSC, the basestations emit a multiplicity of second synchronization signals SSC for asecond step of a synchronization of a base station with a mobilestation. In this process, for UTRA FDD and UTRA TDD the multiplicity ofsecond synchronization signals SSC transmitted in parallel with the PSCare extracted from the same quantity or the same set of 16 prescribedsecond synchronization sequences.

[0077] Depending on the mode or modes in which the base stations arebeing operated, however, the multiplicity of second synchronizationsignals SSC that are sent with the PSC are determined by different codesets into which the 16 SSCs are grouped.

[0078] The set of 16 SSCs is grouped in this case into five code sets inthe UTRA TDD, of which four code sets, which include three SSCs in eachcase, are used for synchronization in UTRA TDD, and one code set, whichincludes four SSCs, is not used for synchronization in UTRA TDD. ThreeSSCs of a code set are then emitted in parallel with the PSC for thepurposes of synchronization in the time slots to which a PSCH (PrimarySynchronization Channel) is assigned.

[0079] The grouping of the second synchronization signals into used codesets is performed as follows in this case:

[0080] Code set 1: SSC1, SSC3, SSC5;

[0081] Code set 2: SSC10, SSC13, SSC14;

[0082] Code set 3: SSC0, SSC6, SSC12;

[0083] Code set 4: SSC4, SSC8, SSC15.

[0084] The PSC and SSCs are formed in this case by methods specifiedabove.

[0085] The determination of the temporal position of the firstsynchronization sequence PSC and of the temporal sequence of themultiplicity of second synchronization sequences SSCs is performed inthe mobile stations by means of correlation calculations. In thisprocess, the synchronization sequence of the PSC is compared over theentire frame at each possible position with the received signal,typically by using a so-called matched filter. In the process, allpossible cross correlations of the SSCs with the PSC also occur, and sothe entire cross-correlation function must be investigated in anoptimization of the SSCs. The first synchronization sequence is used fortime slot synchronization, and the multiplicity of secondsynchronization sequences are used for frame synchronization and fordetecting further system parameters.

[0086] In a further refinement of the invention, it is possible toutilize the fact that the following SSCs all have the same peak value inthe CCF with the PSC:

[0087] SSC₁₃, SSC₁₂, SSC₆.

[0088] It follows that there are three different possible selections forthe formation of the code sets (two that are additional to theabovementioned exemplary embodiment), which all permit an(approximately) identical probability of detection. Here, use is made ineach case of one of these SSCs (SSC₁₃, SSC₁₂, SSC₆) in the second codeset. In a preferred refinement, use is made in this case of SSC₆ for thethird code set, in order to achieve a smaller difference in the RMSvalues between the sets. Although, as represented above, the RMS valueis not the primarily decisive criterion, it can nevertheless beadvantageous to make such a selection as a subordinate criterion.

[0089] In a further refinement of the invention, it is taken intoaccount that a frequency error that can typically be approximately 10kHz can occur during the first cell search. In this refinement, theselection of the code sets is then also carried out as a function of theCCF in the case of a frequency error. The selection criterion specifiedabove is then extended to the effect that use is made not of the valuesof the CCF without frequency error, but of the values of the CCF withfrequency error, or to the effect that use is made of a compromisebetween the best code sets with and without frequency error.

[0090] It is taken into account in a further refinement that the SSCs ofa group can be transmitted simultaneously, the individual SSCs beingmodulated, however, with a value from the group {+1, −1, +j, −j}. Inthis embodiment, it is not the properties of the CCF of the individualSSCs that are optimized with the PSC, but the CCF of the variouspossible combinations of the modulated SSCs with the PSC. In this case,the selection can be carried out in a way similar to that describedabove, in particular taking account of the same criteria as describedabove.

[0091] In addition to the variant designs of the invention explainedabove, the scope of the invention includes a multiplicity of furthervariant designs that are not further described here but can easily beput into practice with the aid of the exemplary embodiments explained.

[0092] This application refers to the following documents, specifically:

[0093] [1] Mitsubishi Electric, “Optimised code sets for PSCH in UTRATDD”, 3GPP TSG RAN WG1#13 Tdoc R1-00-0626, Tokyo, Japan, May 22-25, 2000

[0094] [2] Siemens, Texas Instruments, “Generalised Hierarchical GolaySequence for PSC with low complexity correlation using pruned efficientGolay correlations”, TSG-RAN Working Group 1 (Layer 1) Meeting #5, Tdoc567/99, Cheju Island, Korea, 01.-04.06.1999.

[0095] [5] 3rd Generation Partnership Project; Technical SpecificationGroup Radio Access Network; “Spreading and modulation (TDD)”; 3G TS25.223 V3.2.0 (2000-03)

1. A method for synchronizing a receiver with a transmitter, in which afirst synchronization signal with a multiplicity of secondsynchronization signals which are taken from a set of secondsynchronization signals that is subdivided into code sets is transmittedfrom the transmitter to the receiver, in which the multiplicity ofsecond synchronization signals that are transmitted with the firstsynchronization signal is determined by a code set, in which the codesets are grouped into used code sets and at least one unused code set,and in which the set of second synchronization signals is subdividedinto code sets in such a way that the maximum in the peak values of thecross-correlation functions of the second synchronization signals, whichare determined by a used code set, with the first synchronization signalis minimal.
 2. A Method for synchronizing of a receiver with atransmitter, in which the transmitter transmits a first synchronizationsignal with a multiplicity of second synchronization signals, themultiplicity of second synchronization signals that can be transmittedjointly being determined by a grouping of second synchronization signalsinto code sets, and the code sets being formed in such a way that themaximum in the peak values of the cross-correlation functions of thesecond synchronization signals with the first synchronization signal isminimal.
 3. A method for selecting a multiplicity of secondsynchronization signals that are transmitted jointly with a firstsynchronization signal, in which the multiplicity of secondsynchronization signals are selected from a set of secondsynchronization signals, in which the set of second synchronizationsignals is subdivided into code sets, in which the code sets are groupedinto used code sets and at least one unused code set, in which the setof second synchronization sequences is subdivided into code sets in sucha way that the maximum in the peak values of the cross-correlationfunctions of the second synchronization signals, which are contained ina used code set, with the first synchronization signal is minimal. 4.The Method as claimed in one of the preceding claims for use in the TDDmode of a UMTS system.
 5. The method as claimed in one of the precedingclaims, in which all the synchronization signals of the set of secondsynchronization signals are used for synchronization in the FDD mode ofthe UMTS system.
 6. The method as claimed in one of the precedingclaims, in which the first synchronization signal is a hierarchicsequence, and in which the second synchronization signals can beobtained in each case by the positional multiplication of the firstsynchronization signal by in each case one row of a Hadamard matrix. 7.The method as claimed in one of the preceding claims, in which thesynchronization signals can be formed in the following way: the firstsynchronization signal C_(p) is determined by the followingrelationship: C_(p)=<y(0),y(1),y(2), . . . , y(255)>, wherein it holdsthat: y=(1+j)×<a,a,a,−a,−a,a,−a,−a,a,a,a,−a,a, a,a,a>, wherin it holdsthat: −a=<x₁, x₂, x₃, . . . , x₁₆>=<1, 1, 1, 1, 1, 1, −1, −1, 1, −1, 1,−1, 1, −1, −1, 1>; 16 second synchronization signals {C₀, . . . , C₁₅)are determined by the following relationship: C_(i)=C_(SCH, i), i=0, . .. , 15, wherein it holds that: C_(SCH, i)=(1+j)×<h_(m)(0)×z(0),h_(m)(1)×z(1), h_(m)(2)×z(2), . . . , h_(m)) (255)×z(255)>, wherein itholds that: m=(16×i) the nth Hadamard sequence h_(n) is a series of aMatrix H₈, which can be formed recursively by means of the followingrelationship: H₀ = (1) ${H_{k} = \begin{pmatrix}H_{k - 1} & H_{k - 1} \\H_{k - 1} & {- H_{k - 1}}\end{pmatrix}},{k \geq 1}$

, the numbering beginning at the top with zero, n=0, 1, 2, . . . , 255;h_(m)(i) and z(i) denote the ith symbol of the sequence h_(m) and z,respectively, wherein i=0, 1, 2, . . . , 255 and i=0 corresponds to thesymbol at far left.
 8. The method as claimed in one of the precedingclaims, in which the used code sets are defined as follows: Code set 1:SSC1, SSC3, SSC5; Code set 2: SSC10, SSC13, SSC14; Code set 3: SSC0,SSC6, SSC12; Code set 4: SSC4, SSC8, SSC15.
 9. The method as claimed inone of the preceding claims, in which the temporal position of the firstsynchronization sequence and the temporal position of the multiplicityof second synchronization sequences are determined at the receiving endby means of correlation calculations.
 10. The method as claimed in oneof the preceding claims in which the first synchronization sequence isused at the receiving end for time slot synchronization, and themultiplicity of second synchronization sequences is used for framesynchronization.
 11. The method as claimed in one of the precedingclaims, in which in the case of the minimization criterion the maximumin the peak values of the cross-correlation functions of the secondsynchronization signals, which are determined by a used code set, isalso taken into account with the aid of the first synchronization signalin conjunction with at least one frequency error.
 12. The method asclaimed in one of the preceding claims, in which in the case of aplurality of alternatives with the same maximum in the peak values ofthe the cross-correlation functions of the second synchronizationsignals, which are determined by a used code set, with the firstsynchronization signal, the RMS value of this cross-correlation functionis minimized as subordinate criterion.
 13. The method as claimed in oneof the preceding claims, in which the maximum in the peak values of thecross-correlation functions is minimized by modulated superpositions ofsecond synchronization signals, which are determined by a used code set,with the first synchronization signal.